Catheter-based surgery is advantageously used in various connections to treat body organs with minimal incision size and clearance of the organs. As an example, cardiac arrhythmias may be treated by various catheter-based ablation techniques to destroy arrhythmogenic parts of the cardiac tissue. Specifically, radio-frequency (RF) ablation, high intensity focused ultrasound (HIFU) or cryo-ablations of the tissue are commonly used.
In connection with the ablation process of cardiac tissue, it has recently been realized that the contact force between an ablation catheter's tip and the cardiac tissue is a highly important variable that must be controlled. It has been shown that the contact force is a determinant with respect to the lesion size, cf. “Novel Contact Force Sensor Incorporated in Irrigated Radio frequency Ablation Catheter Predicts Lesion Size and Incidence of Steam Pop and Thrombus”, Circ Arrhythmia Electrophysiol, 2008 by Yokoyama et al. Too great a contact force may lead to unnecessary damage of healthy tissue, whereas too low a contact force may lead to the creation of incomplete lesions. Moreover, the risk of complications increases dramatically with contact force, in particular with respect to the risk of causing stream pops and thrombus in connection with the ablation. Additionally by applying a too high contact force, the cardiac wall may be affected in a way which leads to electro-anatomic mapping registration errors, cf. “A systematical analysis of in vivo contact forces on virtual catheter tip/tissue surface contact during cardiac mapping and intervention”, J Cardiovasc Electrophysiol, 2008 by Okumura et al.
The published US patent application 2008/0009750 A1 discloses a catheter for diagnosis or treatment of a vessel or organ. The catheter has in its distal end region incorporated a tri-axial force sensor for detecting the contact force. The force sensor comprises a housing and a plurality of optical fibers in the housing that measure changes in light intensity resulting from deformations of the housing. The deformation is caused by forces applied at the distal extremity of the catheter. The tri-axial force sensor and associated fibers take up space in the distal region of the catheter, moreover a light source is required which adds to the cost of the device.
There is still a need in the art for improved equipment suitable for use in connection with catheter-based surgery.